tree 7d0c03dd9bc1890eed1fef4987226f6aca6ff0d8
parent b77b5fdd052e7ee61b35164abb10e8433d3160e8
author Andrew Price <anprice@redhat.com> 1615811040 +0000
committer Andreas Gruenbacher <agruenba@redhat.com> 1615818762 +0100

gfs2: Flag a withdraw if init_threads() fails

Interrupting mount with ^C quickly enough can cause the kthread_run()
calls in gfs2's init_threads() to fail and the error path leads to a
deadlock on the s_umount rwsem. The abridged chain of events is:

  [mount path]
  get_tree_bdev()
    sget_fc()
      alloc_super()
        down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); [acquired]
    gfs2_fill_super()
      gfs2_make_fs_rw()
        init_threads()
          kthread_run()
            ( Interrupted )
      [Error path]
      gfs2_gl_hash_clear()
        flush_workqueue(glock_workqueue)
          wait_for_completion()

  [workqueue context]
  glock_work_func()
    run_queue()
      do_xmote()
        freeze_go_sync()
          freeze_super()
            down_write(&sb->s_umount) [deadlock]

In freeze_go_sync() there is a gfs2_withdrawn() check that we can use to
make sure freeze_super() is not called in the error path, so add a
gfs2_withdraw_delayed() call when init_threads() fails.

Ref: https://bugzilla.kernel.org/show_bug.cgi?id=212231

Reported-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>